1. Field of the Invention
The present invention relates to an electrophoretic display and a method of driving the same, and more particularly, to an electrophoretic display capable of displaying frames without image-edge residual and a method of driving the same.
2. Description of the Prior Art
Because flat panel displays (FPDs) have advantages of thin appearance, low power consumption, and low radiation, various kinds of flat panel displays have been developed and widely applied in a variety of electronic products such as computer monitors, mobile phones, personal digital assistants (PDAs), or flat panel televisions. Among them, electrophoretic displays (EPDs), also known as electronic papers, have gained more and more attention due to further advantages of thinner feature, flexible body, and easy-to-carry property. In general, the electrophoretic display comprises a gate driving circuit, a data driving circuit and plural pixels. The gate driving circuit is employed to provide a plurality of gate signals. The data driving circuit is employed to provide a plurality of data signals. Each of the pixels includes a data switch, an electrophoretic medium and plural charged particles suspended in the electrophoretic medium. The color of the charged particles is different from that of the electrophoretic medium. The data switch provides a control of writing a corresponding data signal according to a corresponding gate signal, for changing the voltage difference across opposite sides of the electrophoretic medium. And the voltage difference across opposite sides of the electrophoretic medium can be employed to create an electric field for adjusting the position of the charged particles in the electrophoretic medium. Accordingly, the grey level of each pixel can be set according to the suspension depth of the charged particles in the electrophoretic medium.
FIG. 1 is a schematic diagram showing a prior-art method of driving an electrophoretic display. As shown in FIG. 1, during the time of displaying an Nth frame, both the ith pixel and the (i+1) th pixel are employed to display a grey level of black. And the common voltage Vcom and the pixel voltages VDi, VDi+1 are all set to be a positive voltage Vpos for maintaining the grey level of black, i.e. the charged particles of the ith and (i+1) th pixels are retained to suspend in a position nearby the pixel electrodes 101, 102 within the electrophoretic medium 190. During the time of displaying an (N+1) th frame, the common voltage Vcom is switched to a negative voltage Vneg, the ith pixel is employed to display a grey level of white, and the (i+1) th pixel is employed to display the grey level of black. That is, the grey level of the ith pixel is switched from black color to white color while the grey level of the (i+1) th pixel maintains black color. In the meantime, the pixel voltage VDi+1 is switched to the negative voltage Vneg following a change of the common voltage Vcom. In view of that, the charged particles of the (i+1) th pixel are still retained to suspend in the position nearby the pixel electrode 102 within the electrophoretic medium 190. Besides, the pixel voltage VDi retains the positive voltage Vpos, and the electric field, which is created based on the positive voltage Vpos of the pixel electrode 101 and the negative voltage Vneg of the common electrode 103, moves the charged particles of the ith pixel towards a position nearby the common electrode 103 within the electrophoretic medium 190.
During the time of displaying an (N+2) th frame, the common voltage Vcom is switched to the positive voltage Vpos, both the ith pixel and the (i+1) th pixel are employed to display the grey level of black. That is, the grey level of the ith pixel is switched from white color to black color while and the grey level of the (i+1) th pixel maintains black color. In the meantime, the pixel voltage VDi+1 is switched to the positive voltage Vpos following a change of the common voltage Vcom. In view of that, the charged particles of the (i+1) th pixel are still retained to suspend in the position nearby the pixel electrode 102 within the electrophoretic medium 190. Besides, the pixel voltage VDi is switched to the negative voltage Vneg, and the electric field, which is created based on the negative voltage Vneg of the pixel electrode 101 and the positive voltage Vpos of the common electrode 103, moves the charged particles of the ith pixel towards the position nearby the pixel electrode 101 within the electrophoretic medium 190. It is noted that, in the display setting process of the (N+2) th frame, the electric field created around the edge between the pixel electrode 101 and the pixel electrode 102 is dispersed significantly due to the positive voltage Vpos of the pixel electrode 102. For that reason, in the process of changing the grey level of the ith pixel from white color to black color, some charged particles 199 of the ith pixel, which are suspended in a position close to the edge between the ith and (i+1) th pixels, are actually not moved towards the position nearby the pixel electrode 101, resulting in an image-edge residual phenomenon and degrading the display quality of the (N+2) th frame.
FIG. 2 is a schematic diagram showing another prior-art method of driving an electrophoretic display. As shown in FIG. 2, during the time of displaying an Nth frame, both the ith pixel and the (i+1) th pixel are employed to display a grey level of white. And the common voltage Vcom and the pixel voltages VDi, VDi+1 are all set to be a negative voltage Vneg for maintaining the grey level of white, i.e. the charged particles of the ith and (i+1) th pixels are retained to suspend in a position nearby the common electrode 103 within the electrophoretic medium 190. During the time of displaying an (N+1) th frame, the common voltage Vcom is switched to a positive voltage Vpos, the ith pixel is employed to display a grey level of black, and the (i+1) th pixel is employed to display the grey level of white. That is, the grey level of the ith pixel is switched from white color to black color while the grey level of the (i+1) th pixel maintains white color. In the meantime, the pixel voltage VDi+1 is switched to the positive voltage Vpos following a change of the common voltage Vcom. In view of that, the charged particles of the (i+1) th pixel are still retained to suspend in the position nearby the common electrode 103 within the electrophoretic medium 190. Besides, the pixel voltage VDi retains the negative voltage Vneg, and the electric field, which is created based on the negative voltage Vneg of the pixel electrode 101 and the positive voltage Vpos of the common electrode 103, moves the charged particles of the ith pixel towards a position nearby the pixel electrode 101 within the electrophoretic medium 190.
During the time of displaying an (N+2) th frame, the common voltage Vcom is switched to the negative voltage Vneg, both the ith pixel and the (i+1) th pixel are employed to display the grey level of white. That is, the grey level of the ith pixel is switched from black color to white color while the grey level of the (i+1) th pixel maintains white color. In the meantime, the pixel voltage VDi+1 is switched to the negative voltage Vneg following a change of the common voltage Vcom. In view of that, the charged particles of the (i+1) th pixel are still retained to suspend in the position nearby the common electrode 103 within the electrophoretic medium 190. Besides, the pixel voltage VDi is switched to the positive voltage Vpos, and the electric field, which is created based on the positive voltage Vpos of the pixel electrode 101 and the negative voltage Vneg of the common electrode 103, moves the charged particles of the ith pixel towards the position nearby the common electrode 103 within the electrophoretic medium 190. Similarly, in the display setting process of the (N+2) th frame, the electric field created around the edge between the pixel electrode 101 and the pixel electrode 102 is dispersed significantly due to the negative voltage Vneg of the pixel electrode 102. For that reason, in the process of changing the grey level of the ith pixel from black color to white color, some charged particles 299 of the ith pixel, which are suspended in a position close to the edge between the ith and (i+1) th pixels, are actually not moved towards the position nearby the common electrode 103, resulting in an image-edge residual phenomenon and degrading the display quality of the (N+2) th frame.